What's the most important baseball stat this season? For many young pitchers, it's the number of balls they're allowed to hurl across home plate. That's because Little League Baseball has set a limit on how many pitches players can throw, depending on their age.

"The pitch-count-rule is in place to prevent young arms from overuse," says Chris Downs with the Little League Baseball organization. Since throwing a pitch is not a natural arm motion, over-pitching can result in a torn ulnar collateral ligament. Surgery to replace this piece of tissue, which holds together the ulna and humerus arm bones at the elbow, has been on the rise for high-school pitchers over the last 12 years.

Pitchers that overuse their arm are 36 times more likely to need surgery. The new pitch-count regulation will hopefully help young players stay healthy and off the operating table.